Fix handling of empty SPARK_EXAMPLES_JAR
Quite akka when remote lifecycle logging is disabled.

I noticed when connecting to a standalone cluster Spark gives a bunch
of Akka ERROR logs that make it seem like something is failing.

This patch does two things:

1. Akka dead letter logging is turned on/off according to the existing
   lifecycle spark property.
2. We explicitly silence akka's EndpointWriter log in log4j. This is necessary
   because for some reason that log doesn't pick up on the lifecycle
   logging settings. After a few hours of debugging this was the only solution
   I found that worked.
Provide logging when attempts to connect to the master fail.

Without these it's a bit less clear what's going on for the user.

One thing I realize when doing this is that akka itself actually retries
the initial association. So the retry we currently have is redundant with
akka's.
Responding to Aaron's review
Merge pull request #333 from pwendell/logging-silence

Quiet ERROR-level Akka Logs

This fixes an issue I've seen where akka logs a bunch of things at ERROR level when connecting to a standalone cluster, even in the normal case. I noticed that even when lifecycle logging was disabled, the netty code inside of akka still logged away via akka's EndpointWriter class. There are also some other log streams that I think are new in akka 2.2.1 that I've disabled.

Finally, I added some better logging to the standalone client. This makes it more clear when a connection failure occurs what is going on. Previously it never explicitly said if a connection attempt had failed.

The commit messages here have some more detail.
SPARK-1005 Ning upgrade
Made java options to be applied during tests so that they become self explanatory.
Add warning to null setJars check
Clarify spark.cores.max

It controls the count of cores across the cluster, not on a per-machine basis.
Change protobuf version for yarn alpha back to 2.4.1
Merge pull request #330 from tgravescs/fix_addjars_null_handling

Fix handling of empty SPARK_EXAMPLES_JAR

Currently if SPARK_EXAMPLES_JAR is left unset you get a null pointer exception when running the examples (atleast on spark on yarn).  The null now gets turned into a string of "null" when its put into the SparkConf so addJar no longer properly ignores it. This fixes that so that it can be left unset.
Merge pull request #342 from tgravescs/fix_maven_protobuf

Change protobuf version for yarn alpha back to 2.4.1

The maven build for yarn-alpha uses the wrong protobuf version and hence the generated assembly jar doesn't work with Hadoop 0.23.  Removing the setting for the yarn-alpha profile since the default protobuf version is 2.4.1 at the top of the pom file.
Merge pull request #341 from ash211/patch-5

Clarify spark.cores.max in docs

It controls the count of cores across the cluster, not on a per-machine basis.
Merge pull request #338 from ScrapCodes/ning-upgrade

SPARK-1005 Ning upgrade
Merge pull request #340 from ScrapCodes/sbt-fixes

Made java options to be applied during tests so that they become self explanatory.
Fix test breaking downstream builds
Merge pull request #343 from pwendell/build-fix

Fix test breaking downstream builds

This wasn't detected in the pull-request-builder because it manually sets SPARK_HOME. I'm going to change that (it should't do this) to make it like the other builds.